A conventional interposer is disclosed in U.S. Pat. No. 6,538,214, for example.
FIG. 8 shows the structure of the interposer disclosed in U.S. Pat. No. 6,538,214. Referring to FIG. 8, the interposer 100 includes a ceramic substrate 101 provided with a plurality of conductive holes 102, terminals 103 connected to the conductive holes 102 and arranged on both sides of the substrate 101, and a plurality of probes 104 connected to the terminals 103. On a tip of each probe 104, a contact 105 is provided.
Typical interposers have a similar structure to the one discussed above. Because the substrate 101 is made of ceramic, the formation of the conductive holes necessarily involves drilling or sandblasting the substrate to form through holes and making the through holes conductive, and therefore it is impossible to form conductive holes having a small dimension. As a result, probes cannot be arranged at high density on the ceramic substrate.